Second venturi insert providing air/fuel mixture velocity enhancement

Abstract

A carburetor (1) having an existing venturi upstream of a throttle plate (7) and a bore (17) downstream of a throttle plate (7) is provided with a second venturi (14) which increases airflow velocity and promotes fuel atomization. An aerodynamic piece or wing (15) is mounted to the top of the venturi to further define the airflow path and to prevent the downstream fuel / air mixture (10) from losing velocity after passing the throttle plate. The wing (15) includes a first set of tabs (41, 42) to secure the wing to the engine intake manifold and as second set of tabs (43, 44) to secure the combined wing (15) and venturi to an oversized carburetor bore. A cutout (21) in the venturi (14) prevents interference with the carburetor fuel jet (5). The wing (15) may be formed with a specially shaped trailing edge (51) in order to accommodate the contours of the throttle plate.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to the field of carburetion, and more particularly to the field of carburetor venturi structures and accessories. DESCRIPTION OF RELATED TECHNOLOGY [0002] A carburetor is a device for mixing air and fuel in an internal combustion engine in order to provide a combustible fluid for introduction into a cylinder or other combustion chamber. The carburetor typically has a central bore that is obstructed by a throttle plate which, depending upon the position of the throttle plate admits relatively more or less of the fuel / air mixture into the subsequent or downstream venturi portion of the carburetor. For relatively higher powered engines, the carburetor bore is relatively larger in diameter because a relatively greater amount of fuel and air is needed to support the combustion process that generates the higher power. However, at relatively lower throttle settings, a large bore carburetor becomes relatively inefficient ...

AI Technical Summary

Benefits of technology

[0012] The wing component tends to restrict the air flow to the bottom half of the carburetor bore by preventing the air flow from drifting or looping upwardly toward the top of the carburetor bore when the throttle is only partially open. The ramp component acts as a second venturi which further accelerates the air. The higher velocity of the airflow addresses a number of issues. The throttle response is more nearly instantaneous due to the higher air velocity present at partial throttle settings. This characteristic is valuable in a sport vehicle as the rider is able to accelerate more rapidly as a result of a relatively greater rate of engine power increase as the throttle is opened. The absolute value of the peak engine power produced during the first half of the throttle plate travel is also increased.

[0013] The vehicle operator is able to momentarily elevate the front of the vehicle solely by manipulation of the throttle, as may be required, for example, in order to negotiate bumps, inclines, gaps or rough areas. The rider is also able to steer in reliance on the improved throttle response. Engine temperature stabilize relatively more quickly due to the improved fuel atomization resulting from the higher airflow velocity. The improved fuel atomization also contributes to more thorough fuel combustion, resulting in a decrease in harmful emissions.

[0014] The present invention addresses the erratic idling problem by properly atomizing the relatively dense, moist fuel with a high velocity air column. Fuel is forced along the ramp by the high velocity air column. The fuel is then forced off of the end of the ramp, becoming airborne and quickly atomizing. The effect of the ramp is to substantially reduce the capillary action of flowing, liquid fuel which can produce streaking and puddling. Since the airflow is prevented from flowing upwardly after passing the carburetor slide, the fuel / air mixture tends to flow along a relatively straight path at a relatively higher rate of speed. The second venturi formed by the ramp tends to further increase the air flow velocity.

Problems solved by technology

However, at relatively lower throttle settings, a large bore carburetor becomes relatively inefficient because the smaller volume of the fuel / air mixture occupies the entire large bore volume, thereby reducing both turbulence and mixture velocity and promoting poor mixing of the fuel and air.

A relatively smaller carburetor delivers quick and stable power at the low end while lacking sufficient fuel / air delivery at the midrange and top end due to the limited flow capability of the smaller bore.

A larger carburetor delivers the desired power from the midrange to the top end while lacking stability, responsiveness and fuel efficiency at the low end due to the relatively slower air speeds associated with lower throttle settings.

Since the vast majority of engines operate with a single carburetor having a fixed bore, most engines have to some degree a poor throttle response otherwise known as throttle lag.

This is a commonly encountered problem with many types of sporting vehicles such as motorcycles, all terrain vehicles, scooters, go carts and personal watercraft.

A problem often associated with flat slide type carburetors is called fuel puddling or streaking which occurs when liquid fuel exits the pilot jet, flows along the carburetor body and into the engine while remaining in a liquid state.

This is a result of insufficient air velocity within the carburetor bore that is needed to promote atomization of the fuel into airborne droplets.

After a sufficient quantity of fuel has collected, some of it may (or may not) vaporize at random intervals causing an excessive amount of fuel to be instantaneously sent to the combustion chamber.

Another frequently encountered problem is an erratic idle response that causes the engine speed to fluctuate higher and then lower, or to maintain an engine speed that is higher than an acceptable idle speed even though the throttle has been fully returned to its lowest idle position.

Large bore single and twin cylinder two cycle engines are often subject to the erratic idle syndrome.

. . air leaking around the flat slides themselves, and this inconsistency is very likely the cause of the occasional high idle speeds .

The lack of atomization is due to the relatively low air speeds at partial throttle.

While the Boyesen device accomplishes the goal of reducing fluctuations in the velocity of the fuel / air mixture, the device occupies a substantial amount of cross sectional area within the air flow passageway, leading inevitably to absolute velocity losses induced by its presence.

Neither of the foregoing schemes is amenable to modifying an existing carburetor in the field due to their relative complexity and need for specialized tooling.

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